Spirit level



April 27, 1943. E. D. BALL SPIRIT LEVEL Filed June 5, 1942 1g 1SEEEEEEEQEEE I Patented Apr. 27, 1943 srnnr LEVEL Edgarv Dale Ball,Derby, England, assignor of onehalf to George H. AlexanderMachinery'Limited, Birmingham, England ApplicationiJnne-S, 1942*, SerialNo. 445,935 In Great Britain June .18, 1941 4 Claims.

' The object of this invention is to facilitate the construction ofhigh-class spirit levels, and also to enable the sensitivity of suchlevels to be readily adjusted.

The invention comprises the combination of a hollow body part, asubstantially straight glass or other suitable tube containing theliquid and bubble, and'means within the body part for flexing the tube.

The invention also comprises the combination with a spirit level asspecified in the preceding paragraph, of externally operable means foradjusting the fiexure of the tube.

In the accompanying sheet of explanatory drawings:

Figures 1, 2 and 3 are respectively a sectional side elevation, an endelevation, and a plan of a spirit level constructed in accordance withthe invention.

Figure 4 is a section on the line 4 i of Figure 1.

In carrying the invention into effect as shown, I employ a hollowrectangular metal or other rigid body part 0. having its upper portionmade to an open channel-like form. Arranged longitudinally within thechannel-like upper portion of the body part a is a substantiallystraight glass or other transparent tube b' containing the usual liquidand bubble, the latter being indicated by c, and being visible throughthe open upper side of the body part. The tube b is supported by apressure bar at which is also arranged longitudinally within thechannel-like upper portion of the body part a, and which is grooved toaccommodate the adjacent portion of the tube, the latter being arrangedto project beyond both ends of the pressure bar. Any convenient meansare employed for preventing endwise movement of the pressure bar dwithin the body part a. Thus, the pressure bar at may be provided asshown with a laterally projecting pin e which engages a vertical groovein the adjacent portion of the body part. The tube b is retained withinthe body part a by a pair of abutment pieces g which embrace and supportthe upper sides of the end portions of the tube, and the pressure bar (1bears at its ends (either directly or through the agency of pads h) onthe underside of the tube at positions spaced from the ends of the tubethe arrangement being such that the tube can be flexed slightly by thepressure exerted on it by the pressure bar. For enabling this pressureto be varied the pressure bar it rests on a longitudinally adjustablewedge piece 2' in the form of a slightly tapered bar, this wedge piecebeing slidably fitted in the bottom of the chainnel-like upper portionof the body part a. The taper of the wedge piece 2' is so slight that itcannot easily be illustrated, but it is suiiicient to enable therequired flexing of the tube b to be effected by the pressure bar d uponthe wedge piece being moved to an appropriate extent relatively to thepressure bar, the distance between the positions at which the pressurebar acts onthe tube being such that the intervening portion of the tubewhen flexed has a true arcuate form.

When, as in the example shown, it is desired that the user of the spiritlevel above described shall be able to adjust the flexure of the tube band consequently the sensitivity of the level, I mount in one end of thebody part a and in alignment with the wedge piece i, a, rotatable butaxially immovable screw 7 which at its inner end engages'a screwthreaded hole k in the adjacent end of the wedge piece, the outer end ofthe screw being provided with a head m whereby it can be rotated. Axialmovement of the screw 7' is prevented by the engagement of aspring-loaded ball or other detent n in the body part a with acircumferential groove 0 in the screw. The effect of rotating the screw:i is to move the wedge piece 2' relatively to the pressure bar d and soalter the amount of fiexure of the tube b. For indicating the amount ofmovement imparted to the wedge piece 1', the latter may be provided atone side with a scale 17 which can be seen through an opening q in thebody part a, and which is movable with the wedge piece relatively to anindex mark on the body part. A stop 1* in the body part a at the end ofthe wedge piece 2' remote from the adjusting screw 7 serves by contactwith this end of the wedge piece to determine one limit position of thewedge piece.

To enable fine adjustment in the initial setting of the tube 11 to beobtained, the abutment pieces 9 are slidably adjustable in inclinedguides s formed on or secured to the ends of the body part a. Theseguides s are of dove-tail form and are slit longitudinally whereindicated by t to provide parts between which the corresponding abutmentpieces can be secured under the action of screws u passing transverselythrough the said parts. For enabling the abutment pieces 9 to beindividually adjusted, screws 11 engaging screw threaded holes w in theguides s are provided with collars a: which engage recesses 11 in theabutment pieces, so that axial movement of either of these screws isaccompanied by adjusting movement of the corresponding abutment piece.The adjusting screws and holes w are situated between the split parts ofthe corresponding guides s, so that when these parts are caused by thesecuring screws u to grip the abutment pieces 9 they also serve to gripand secure the adjusting screws 12.

In the example shown the body part a is formed beneath its upperchannel-like portion,

with a longitudinal opening 2 which serves to reduce the weight of thelevel, the under surface 7 of the body part being formed withintersecting grooves if desired.

By this invention I am able greatly to facilitate the construction ofspirit levels required for use in accurate measurements, and to impartconveniently to the level any desired degree, of

sensitivity. Moreover I am able to make the sensitivity variable by theuser so that the one level can be readily adapted to differentrequirements.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A spirit level comprising the combination of a hollow body part, asubstantially straight tube containing liquid and a visible bubble, andmeans within the body part for flexing the tube.

2. A spirit level as claimed in claim 1 and having externally operablemeans for adjusting the flexure of the tube.

3. A spirit level having in combination a hollow body part, asubstantially straight tube containing liquid and a visible bubble, apair of abutment pieces by which the end portions of the tube aresupported at one side of the tube, and means within the body part forflexing the tube, the said means comprising a pressure bar 10 by whichthe opposite side of the tube is supported at positions spaced from theends of the tube, and a wedge piece supported by the body part, thepressure bar being arranged between the tube and the wedge piece.

4; A spirit level having in combination a hollow body part, asubstantially straight tube containing liquid and a visible bubble, apair of abutment pieces by which the end portions of the tube aresupported at one side of the tube,

means within the body part for flexing the tube, the said meanscomprising a pressure bar by which the opposite side of the tube issupported at positions spaced from the ends of the tube, and a wedgepiece supported by the body part,

the pressure bar being arranged between the tube and wedge piece, andscrew means whereby the wedge piece can be moved relatively to thepressure bar for varying the pressure exerted by the bar on the tube.

EDGAR DALE BALL.

